Fun game! I think you should tone down the brain damage effect a bit and make it less frequent, but the idea is pretty cool (also, I recommend only having it change the sprites of the items, it causes weird collisions). I'd also recommend making it so you can only add one wheel to a car at a time as they can stack weirdly. I think it would be a lot of fun as a time attack game where you try to make as much money as possible in a limited time as currently, there's no real point to going fast. The game is really fun when its chaotic and I think you could incentivize that more. I hope you keep working on it, its really interesting!